<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        div {
            /* 给父元素添加flex属性 */
            display: flex;
            width: 100%;
            height: 800px;
            background-color: aquamarine;
            /* flex-direction: column; */
           /* justify-content设置主轴上子元素的排列方式 */
           /* justify-content: flex-start;默认 */
           /* justify-content: flex-end; */
           /* 在主轴居中对齐（如果主轴是！！x轴！！则水平居中） */
           /* justify-content: center; */
           /* 平分剩余空间 */
           justify-content: space-around;
           /* 先两边贴边再平分剩余空间（重要） */
           /* justify-content: space-between; */
        }

        span{
           width: 150px;
           height: 100px;
           background-color: purple; 
        }
    </style>
</head>

<body>
    <div>
        <span>1</span>
        <span>2</span>
        <span>3</span>
    </div>
</body>

</html>